In the prior art, adoption of the enhanced Physical Downlink Control Channel (ePDCCH) makes it possible to serve more users. Besides, it is noticed that there is a correspondence relationship between the number of Control Channel Elements (CCEs) and ACK/NACK region in Physical Uplink Control Channel (PUCCH). With the increasing number of CCEs, the corresponding PUCCH resources for uplink ACK/NACK might be insufficient. Some techniques have been introduced into the prior art to expect to alleviate the issue of insufficient resources. For example, lowest eCCE index number plus offset, and the like. However, although the lowest eCCE index number plus offset may be applied to a frequency division duplexing (FDD) system, it is not well applicable to a time division duplexing (TDD) system, because the TDD system not only has a one uplink subframe corresponding to one downlink subframe mode, but also has a one subframe corresponding to multiple downlink subframe mode. For example, as shown in FIG. 1, the uplink subframe within the circle corresponds to two downlink subframes, the uplink subframe at the left side of the uplink subframe within the circle corresponds to three downlink subframes, and the right-side uplink subframe corresponds to one downlink subframe, wherein one uplink subframe corresponding to one or more downlink subframes means the ACK/NACK of the one or more downlink subframes are reported in its corresponding uplink subframe. In this occasion, in a TDD system adopting ePDCCH, the lowest eCCE index number plus offset technique cannot be utilized. This issue can be better illustrated with reference to FIG. 2.
FIG. 2 shows a diagram of two downlink subframes provided with ePDCCH. The transversal axis of FIG. 2 represents time domain, while the longitudinal axis represents frequency domain, wherein the ACK/NACK of downlink subframes 1 and 2 are reported in one uplink subframe. In other words, FIG. 2 schematically shows a one uplink subframe corresponding to two downlink subframes mode. In order to serve more users, ePDCCH is added to a PDSCH (Physical Downlink Shared Chanel). However, the currently existing solution is not completely suitable for the TDD system. That is to say, in the TDD system, the existing PDCCH-specific system resource allocation scheme is not suitable for a TDD system with ePDCCH, while the “lowest eCCE index number plus offset” is not well suitable for the TDD system with the ePDCCH either.